Four years ago the National Cancer Institute identified the tumor microenvironment as a priority research area in an effort to expand our knowledge of the cells and factors that normally populate the microenvironment, as well as to advance our understanding of how these microenvironment components interact with tumor cells. [unreadable] [unreadable] The Fourth International Conference on Tumor Microenvironment: Progression, Therapy and Prevention, is timely as many novel concepts have emerged in the field since that time and the contribution of the microenvironment to cancer progression is increasingly recognized. [unreadable] [unreadable] The meeting will be held over 31/2 days and consist of 9 plenary sessions, 6 concurrent symposia, and 1 poster session. Plenary sessions will focus on Gene Expression Regulation in the Tumor Microenvironment, Inflammatory Reactions in the Tumor Microenvironment, Immune Function in the Tumor Microenvironment, Tumor-Associated Stroma and the Extracellular Matrix, Tumor-Endothelium Interaction, Novel Perspectives, Tumor Microenvironment Pharmaceutics (2 sessions), and Targeting the Tumor Microenvironment: Preclinical and Clinical Trials. [unreadable] [unreadable] The organizers' goal is to present a series of state-of-the-art lectures around a unified theme of "The microenvironment and its role in cancer progression, therapy and prevention"; increase the awareness of the scientific community, and in particular more junior investigators and students, of the importance of this field of research in cancer; encourage junior investigators and students to initiate investigations in this area; accelerate translational research by bringing together scientists, clinicians, academicians, and researchers of the industry; and provide ample opportunities for open discussion, scientific interaction, and collaboration among scientists with complementary expertise. [unreadable] [unreadable] To hold another conference on this topic in 2007 is appropriate considering the rapid phase of development of this field of cancer investigation. [unreadable] [unreadable] [unreadable]